Subterranean retorting of shales



March 3, 1953 L p EVANS 2,630,306

SUBTERRANEAN RETORTING OF SHALES Filed Jan. 3, 1952 LOU/5 /2 EVA/v5 BYLSHLE ED Patented Mar. 3, 1953 SUBTERRANEAN RETGRTING OF SHALES Louis P.Evans, Woodbury, N. J., assignor to Socony-Vacuum IOil Company,Incorporated, a corporation of New York Application January 3, 1952,Serial No. 264,'761

6 Claims.

This invention relates to a process for recovering valuable hydrocarbonsfrom hydrocarbonaceous and/or carb'onaceous materials such as shales,coals, and the like by treating deposits thereof underground. Moreparticularly, the present vinvention is concerned with an improvedmethod for subterranean retorting of oil shale to yield shale oil.

It is common practice in the art torecover oils from 'solid roil-bearingor oil-producing materials and particularly "to recover shale oil fromoil shales. As is well recognized, lordinary oil "shale 'does notcontain oil as such but a solid, bitumen type material known as kerogenwhich, when heated, breaks down into gases, petroleum-like liquids, andcarbon.

The recovery of oil from oil shale has hereto- 'fore been accomplishedby heating the 4shale .at elevated temperatures suiicient vto educt theoil and separate it from residual :mineral matter. However, commercialshale retorting operations previously employed have generally beencumbersome and expensive, involving large equipment and voperating costsper unit of shale throughput. Important factors contributing Yto theseeconomic burdens have been poor heat recovery in the retorting systemand the expense, equipment, and time consumed in mining land crushingthe shale, and in subsequently recovering 'the products of retortation.A major object of 'this invention, accordingly, is the .provision of aprocess in which oil shale and the like may be eiciently retortedwithout incurring the large expenditure .for equipment and maintenancerequired bythe prior art methods. A further `object 'is to provide amethod for retorting oil shale 'wherein the loperation is conducted inan eiiicient manner underground and the shale is retorted in place. Astill further Aobject is the provision of an inexpensive process forretorting oil shale aiording convenient means for subsequent recovery ofthe liquid shale oil.

The above and other objects which will be apparent to thoseskilled inthe art are accomplished in accordance with the present invention.

The large deposits of oil shales in the western .part of the UnitedStates, particularly in Colorado, Utah, vand Wyoming, contain contiguousstrata of oil shales ranging from a few feet up to 100 feet inthickness. The instant process takes advantage of thes natural featuresof .the shale deposits, namely, the strata formation, structure, andthickness of the shale deposit, to afford a .resultant economy vincommercial retorting of the shales and handling of the products 'ofretorta'tion.

vOperation of the lprocess described herein comprises driving horizontaltunnels immediately above and below the oil-bearing shale 'strata andydrilling a plurality lof holes vertically through the separating layerof shale to connect Athe horizontal tunnels. A plurality of blocks orbaf- -fles are positioned -at predetermined intervalsin 'each 'of thehorizontal tunnels to provide alternate zones of up .and vdown iiowthrough a series 'of fthe vertically drilled holes interconnecting thehorizontal tunnels. Retorting takes place in the shale bed Iby ignitionof the shale in the vfirst Iseries of vertical holes piercing the .shalebed. Upon initiation of .combustion in this first series, a combustionsupporting gas such as air, or a mixture of air and vrecycle gas, isblown into 'and through the rst series of lvertical holes. The heatthereby `generated is suiiicient to initiate retorting in the subsequent.zones and the retorting proceeds successively through each zone withthe released oil vapors diffusing out into the gas stream. The resultingvgaseous stream of retortation .products iiows alternately up and down`through each series of vertical holes piercing the `shale bed. Shaleoil is "condensed in the colder zones downstream vand drains into thelower of lthe horizontal tunnels -from 'which it rmay be removed bysuitable conduits. While the `downstream shale is preheated with the hotvapor- Ious products of retortation :being emitted from previouslyignited zones, the upstream or spent shale is cooled as a .result of.heat exchange with incoming air or other combustion supporting gas,thereby imparting -a high thermal eiciency to the over-all process.

The invention may be more readily understood by reference to theattached drawing wherein:

Figure 1 represents a vertical section through a high mesa containingstrata -of oil shale,

Figure 2 is a plan view in part of the system shown in Figure 1, takenalong the elevation of the ceiling of tunnel Il hereinafter described,

Figure 3 is similar to Figure 1 but depicts an alternate arrangement forwithdrawal of the released shale oil.

Referring more lparticularly to the drawing and specically to Figure l1thereof, I is the -rock over- .burden .lying lon top-of the strata .of`oil shale to be worked, 2 is a series of stratavof oil shalerepresenting the shale bed to be Worked, and 3 is the country rock lyingbelow the main body .of `shale oil strata. .In .accordance with theinvention, a rhorizontal tunnel 4 is driven immediately above theshalestrata .to be worked. Likewise, a horizontal tunnel 5 is drivenVAimmediately below the `shale strata. .A plurality -of `ver-.ticalholes 6 are drilled or otherwise formed between the two horizontaltunnels. A plurality of baffles 1 are inserted at predeterminedpositions in each of the horizontal tunnels 4 and 5 in such a manner asto provide alternate zones of upward and downward ow through thevertical holes in the shale bed.

The shale in the first of such created zones is ignited by theintroduction of hot combustion gases into the formation through conduit8. After ignition of the shale is started, air or other combustionsupporting gas is forced through conduit S. The gases and vaporousproducts of retortation thereafter alternately flow upward and downwardthrough the vertical holes in each zone of the shale bed, successivelyretorting the shale in each of the zones. The shale oil so releasedundergoes condensation in the cooler downstream zones and ultimately iscollected as a pool IU in the last of the retorting zones. The condensedoil is suitably collected in a depression 01 hole I I formed in theunderlying country rock from which it may be withdrawn through conduitI2. The remaining retort gas containing combustion gas and thenon-condensable portion of the retortation products is withdrawn fromthe lower horizontal tunnel 5 through conduit I3. If desired, a streamof this cool retort gas may be recycled through conduit I4, passingthrough the upper horizontal tunnel 4 and entering the last of theretortation zones wherein it serves to cool the products of retortationformed in such zone and in previous zones, thereby aiding incondensation of the vaporous shale oil. Likewise, a. cool stream ofinert gas may be introduced into the last of the retortation zones tofacilitate condensation. The retort gas not recycled is withdrawn bypump I5 and led through conduit I6. If desired, the retort gas passingthrough conduit I6 may be recycled through conduit 8, the combustibleportion thereof serving as a source of heat for further retortation ofthe shale.

While a series of three vertical holes in each zone have been shown, itwill be realized that any convenient number of such holes may be drilledvertically through the shale bed. As a practical matter, the number ofsuch drilled holes will depend upon the extent and richness of the shaledeposit being worked. In the case of the richer deposits, generally itis preferable to drill a greater number of holes, whereas in the case ofthe relatively poorer deposits, a lesser number of holes will usually besuilicient to exhaust the volatile content of the shale bed beingworked. The holes are usually so spaced that substantially all of thecombustible components present in the shale bed will be removed duringthe retorting process. As a general matter, it will usually be expedientto drill the holes in staggered relationship such as shown in Figure 2of the drawing. It will be noted from such figure illustrating zoneshaving three holes drilled therethrough that the holes are suitably sostaggered that the centers thereof if joined would form an equilateraltriangle. As will further be noted from Figure 2, the holes in alternatezones are alternately spaced so that if the centers of the holes in eachzone were joined, the resulting triangles would alternately pointdownward and upward throughout the series of retorting zones.

An alternate arrangement for collecting the released shale oil is shownin Figure 3. In this embodiment of the process, condensed shale oil iscollected in the bottom of each of the retortng zones in a series ofholes Il drilled in the country rock underlying the shale strata. 'Iheseholes are connected by a common conduitl I8 bored through the countryrock. Condensed shale oil formed in each of the retorting zones collectsin each of the holes I1 and passes through conduit I8 and then outwardlythrough conduit I9 to suitable storage facilities.

The horizontal tunnels immediately overlying and underlying the shalestrata to be worked may be of any desired width, ordinarily dependingupon the size and richness of the shale deposit. As a general matter,the tunnels will usually be or more feet long. The time required tocomplete retorting from the ilrst to the last of the retortation zoneswill depend on the length of the particular shale strata being Worked.As a general rule, for a stratum of approximately 100 feet in length,approximately one week would be required.

The temperature of retorting generated within the shale bed is generallybetween about 800 and about 1500 F. For this reason, the baille 1 usedin the formation of the alternate zones of retortation must be composedof a material which is able to withstand such high temperatures. As apractical matter, the baffles are ordinarily composed of rock obtainedduring the initial drilling and excavation. It will thus be evident thatthere is very little needed in the way of expensive equipment forcarrying out the present process for retortation of shale. Theunderground or in-place retorting of shale carried out in accordancewith the instant process reduces the large mining, crushing, andretorting costs involved in present above ground methods. The instantprocess also aiTords a high thermal eiliciency since the initial hotvaporous products of retortation passing through subsequent zones serveto preheat such zones and also the spent upstream shale serves topreheat the incoming combustion supporting gas being fed to thedown-stream zones. The present process is further advantageous inaffording separation of liquid shale oil from the gaseous products ofretortation by collecting the shale oil underground in a pool or seriesof pools from which it may subsequently be withdrawn.

While the process described herein has been directed particularly to therecovery of shale oil from oil shale, the present invention may beadapted for the recovery of oil from any subterranean oil-containing oroil-producing solid substance. Accordingly, it is to be understood thatthe above description is merely illustrative of preferred embodiments ofthe invention, of which many variations may be made within the scope ofthe following claims without departing from the spirit thereof.

I claim:

l. A process for obtaining shale oil from oil shale stratum in itsnatural position, comprising driving horizontal tunnels immediatelyabove and immediately below said stratum, drilling a plurality of holesvertically through the separating layer of shale to connect saidhorizontal tunnels, positioning a plurality of baiiles at predeterminedintervals in each of the horizontal tunnels to provide interconnectingalternate zones of up and down flow through a series of the verticallydrilled holes between said horizontal tunnels, initiating combustion ofshale in the first of said zones adjacent the exterior of said shalestratum, blowing a combustion supporting gas through said rst zone tobring the same to shale retorting temperature, flowing the resulting hotgaseous products of' retortation alternately up and down through eachseries of vertical holes in subsequent zones whereby the shale in eachof said zones is initially preheated and ultimately the temperaturethereof is raised to such point that retorting of shale proceedssuccessively through each zone with release of shale oil vapors,condensing the shale oil vapors so released and eiiecting collection ofthe resulting liquid shale oil.

2. A process for obtaining shale oil from oil shale stratum in itsnatural position, comprising driving horizontal tunnels immediatelyabove and immediately below said stratum, drilling a plurality of holesvertically through said separating layer of shale to connect saidhorizontal tunnels, the number of said vertical holes being such thatsubstantially all of the combustible components present in the shale bedwill be removed during retorting thereof, inserting a plurality ofbailles at predetermined substantially uniformly spaced intervals ineach of the horizontal tunnels in such fashion as to provideinterconnecting alternate zones of up and down flow through each seriesof the vertically drilled holes between said horizontal tunnels,initiating combustion of shale in the rst of said zones adjacent theexterior of said shale stratum, forem ing a combustion supporting gasunder pressure through said first zone to bring the same to shaleretorting temperature, ilowing the resul-ting h-ot gaseous products ofretortation alternately up and down through each series of verticalholes in subsequent zones whereby the shale in each of said zones isinitially preheated and ultimately the temperature thereof is raised tosuch point that retorting of shale proceeds successively through eachzone with release of shale oil vapors, condensing the shale o-il vaporsso rel-eased in the cooler downstream zones and collecting the resultingliquid shale oil in the form of a pool in the last ofthe retortingzones.

3. A process for subterranean retorting of oil shale in its naturalposition, which comprises driving horizontal tunnels immediately aboveand immediately below strata of oil shale, drilling a plurality of holesvertically through the separating layer of shale to connect saidhorizontal tunnels, positioning `a plurality of baiiles at predeterminedintervals in each of the horizont-al tunnels to provide interconnectingalternate zones of up and down flow through a series of the verticallydrilled holes between 'said horizontal tunnels, initiating combustion ofshale in the rst of said zones Iadjacent the exterior of said shalestrata, blowing la combustion supporting gaseous mixture of air andrecycle gas prepared as hereinafter deined through said iirst zone tobring the same to shale retorting ternperature, flowing the resultinghot gaseous products of retortation Ialternately up land down througheach series of vertical holes in subse quent zones, whereby the shale ineach of said zones is initially preheated and ultimately the temperaturethereof is raised to such .point that retorting oi shale proceedssuccessively through each zon-e with release of shale oil vapor andretort glas, condensing the shale oil vapor so released, effectingcollection of the resulting liquid shale oil, withdrawing a stream ofthe retort gas and recycling lthe 'same for admixture with air to formthe aforesaid combustion supporting gas mixture.

4. A process for obtaining shale oil from oil shale stratum in itsnatural position, comprising drivingk horizontal v tunnels immediatelyabove and immediately below said stratum, drilling a plurality of holesvertically through the separat'-4 ing layer of shale to connect saidhorizontal tunnels, positioning a plurality of baiiies at predeterminedintervals in each of the horizontal tunnels in such fashion as toprovide interconnecting alternate zones of up and down flow through aseries of the vertically drilled holes between said horizontal tunnels,initiating combustion of shale in the rst of said zones adjacent theexterior of said shale stratum, blowing a combustion supporting gasthrough said first zone to bring the same to shale retortingtemperature, flowing the resulting hot gaseous products of retortationalternately up and down through each series of vertical holes insubsequent zones, whereby the shale in each of said zones is initiallypreheated and ultimately the temperature thereof is raised to such pointthat retorting of shale proceeds successively through each zone withrelease of shale oil vapors, condensing the shale oil vapors soreleased, effecting collection of the resulting liquid shale oil in thebottom of the lower horizontal tunnel, withdrawing a stream ofnon-condensable retort gas from the lower horizontal tunnel andrecycling said stream to the upper horizontal tunnel, whereby gaseousretortation products entering the last of said zones are cooled, therebyfacilitating condensation of the condensable portion of said retortationproducts.

5. A process for subterranean retorting of oil shale, which comprisesdriving horizontal tunnels immediately above and immediately below anatural deposit of oil shale stratum, drilling a plurality of holes instaggered relationship vertically through the separating layer of shaleto connect said horizontal tunnels, the number of said vertical holesbeing such that substantially all of the combustible components presentin the shale bed being worked will be removed upon retortation,inserting a plurality of baffles in substantially uniformly spacedpredetermined intervals in each -of the horizontal tunnels to provideinterconnecting alternate zones of up and down flow thro-ugh a series ofthe vertically drilled holes between said horizontal walls, initiatingcombustion of shale in the iirst of said zones adjacent the exterior ofsaid shale stratum, blowing a combustion supporting gas into said iirstzone to bring the same to shale retorting temperature, owing theresulting hot gaseous products of retortation alternately up and downthrough each series of vertical holes in subsequent zones, whereby theshale in each of said zo-nes is initially preheated and ultimately thetemperature thereof is raised to such point that retorting of shaleproceeds successively through each zone with release of shale oilvapors, condensing the shale oil vapors so released, effectingcollection of the resulting liquid shale oil in a series of pools in thebottom of each of said retorting zones and withdrawing a stream ofliquid shale oil from, each of said pools.

6. A process for obtaining shale oil from oil shale stratum in itsnatural position, comprising driving horizontal tunnels immediatelyabove and immediately below said stratum, drilling a plurality of holesvertically through the separating layer of shale to connect saidhorizontal tunnels, positioning a plurality of bales at predeterminedintervals in each of the horizontal tunnels to provide interconnectingalternate zones of up and down flow through a series of the vertically 7drilled holes between said horizontal tunnels. initiating combustion ofshale in the rst of saidzones adjacent the exterior of said shalestratum. blowing a combustion supporting gas through said first zone tobring the same to shale retorting temperature, blowing the resulting hotgaseous products of retortation alternately up and down through eachseries of vertical holes in subsequent zones, whereby the shale in eachof said zones is initially preheated and ultimately the temperaturethereof is raised to such point that retorting of shale proceedssuccessively through each zone with release of shale oil vapors,introducing a cold inert gaseous stream into the last of said zones tofacilitate condensation of shale 15 oil vapors within said zone andeffecting collection of liquid shale oil as a. pool in the bottom ofsaid zone.

LOUIS P. EVANS.

REFERENCES CITED The following references are of record in the ille ofthis patent:

UNITED STATES PATENTS Number Name Date 1,269,747 Rogers June 18, 19181,422,204 Hoover et al July 11, 1922 1,919,636 Karrick July 25, 19332,481,051 Uren Sept. 6, 1949

1. A PROCESS FOR OBTAINING SHALE OIL FROM OIL SHALE STRATUM IN ITSNATURAL POSITION, COMPRISING DRIVING HORIZONTAL TUNNELS IMMEDIATELYABOVE AND IMMEDIATELY BELOW SAID STRATUM, DRILLING A PLURALITY OF HOLESVERTICALLY THROUGH THE SEPARATING LAYER OF SHALE TO CONNECT SAIDHORIZONTAL TUNNELS, POSITIONING A PLURALITY OF BAFFLES AT PREDETERMINEDINTERVALS IN EACH OF THE HORIZONTAL TUNNELS TO PROVIDE INTERCONNECTINGALTERNATE ZONES OF UP AND DOWN FLOW THROUGH A SERIES OF THE VERTICALLYDRILLED HOLES BETWEEN SAID HORIZONTAL TUNNELS, INITIATING COMBUSTION OFSHALE IN THE FIRST OF SAID ZONES ADJACENT THE EXTERIOR OF SAID SHALESTRATUM, BLOWING A COMBUSION SUP-